Cyclin-dependent kinase-like 5 (CDKL5) mutation/deficiency, also known as atypical Rett syndrome, is a debilitating postnatal neurological disorder that occurs worldwide in 1 of every 17,000 to 38,000 female births. Males are also affected at a lower incidence. This disorder is not limited to ethnic or racial origin. Symptoms of CDKL5 mutation/deficiency range from mild to severe and present as early onset seizure, cognitive disability, hypotonia as well as autonomic, sleep and gastrointestinal disturbances. Symptoms of disease result from the deficiency of a functional CDKL5 protein.
Mutations in the X-linked CDKL5 gene or deficiencies in the CDKL5 protein in individuals are implicated in the development of atypical or congenital Rett syndrome. See Bertani et al., J. biol. Chem. 2006, 281:32048-320 56, Scala et al., J. Med. Gen., 2005. 42:103-107, and Kalscheuer et al., Am. J. Hum. Genet. 2003. 72:1401-1411. The CDKL5 gene is located on the X-chromosome and encodes a protein that is essential for normal brain development and function. CDKL5 protein is a multifunctional protein that has multiple effects in a neuronal cell. For example, CDKL5 can act as a kinase and phosphorylate MeCP2. Girls affected by the CDKL5 mutations or deficiencies typically have a normal prenatal history; irritability and drowsiness in the perinatal period; early-onset epilepsy with onset before 5 months of age, Rett-like features, including deceleration of head growth, stereotypies, poor to absent voluntary hand use, and sleep disturbances, and severe mental retardation with poor eye contact and virtually no language. See Bahi-Buisson and Bienvenu. 2012. Mol. Syndromol. 2:137-152.
Current treatments for CDKL5 mutations/deficiencies are primarily focused on managing symptoms. However, there are currently no treatments that improve the neurological outcome of subjects with CDKL5 mutations or deficiencies. As such, there exists a need for development of therapies for treating the CDKL5 mutations and deficiencies.